Why is my cat’s third eyelid showing?

A cat’s third eyelid, or nictitating membrane, is a fold of tissue in the inner corner of the eye near the nose that helps protect the eye and moisten the mucous membrane covering the eye. The third eyelid doesn’t usually stay visible, or elevated, in a healthy cat. A third eyelid that’s always visible is a sign of many medical conditions and should be taken seriously by cat owners. Read on to learn:

• Why cats have a third eyelid
• Conditions that cause an elevated third eyelid in cats
• How the cause of a raised third eyelid is diagnosed and treated

A healthy cat’s third eyelid may be temporarily raised when a cat is sleepy or recovering from anesthesia. The third eyelid may stay elevated as a result of eye injuries, such as corneal ulceration or foreign bodies in the eye. Viral infections, neurological disorders, eye infections, and a prolapsed nictitans gland can also result in an elevated third eyelid. If your cat’s third eyelid is consistently raised, you should seek veterinary attention. Treatment options vary widely depending on the underlying cause.

The third eyelid, or nictitating membrane (nictitans), is a whitish-pink eyelid in cats that helps keep the eye moist and adds an extra layer of protection for the eye. A healthy third eyelid isn’t usually visible other than as a small, light pink membrane arising from the inner corner of a cat’s eye near the nose. A cat cannot voluntarily raise its third eyelid, but the nictitans rises on its own when the eyeball retracts into the eye socket. This provides protection for the eye and can occur reflexively when a cat flinches away from something or part of the eye is inflamed or painful. Various overall health and eye conditions can also make the third eyelid protrude abnormally.

Is it abnormal for a cat’s third eyelid to show?

In the majority of cases, a cat’s third eyelid should not show beyond a small fold of tissue in the inner corner of the eye. A temporarily raised third eyelid can sometimes be seen just before or after a cat sleeps. A consistently raised third eyelid is a sign something may be wrong, even if the cat is not experiencing other symptoms.

In most cases, a consistently elevated third eyelid is a sign of disease or eye injury, even if there are no other apparent clinical signs. The exception is if a cat’s third eyelid is raised when they’re sleepy or have recently been sedated or woken from anesthesia.

“The third eyelid becomes prominent when something makes the eyeball retract into the socket or makes the membrane so swollen it pushes the eyeball out of the way,” states Dr. Jo Myers, a veterinarian on the Vetster platform. “A cat flinching from a fight or out of fear will reflexively raise their third eyelid for a brief moment, but the third eyelid may stay elevated and be especially visible under a number of different circumstances.”

Sleepiness or use of anesthesia

A cat’s third eyelid may be more visible when a cat is sleepy or right after they wake up. In addition, a cat being sedated or recovering after the use of anesthesia may also have elevated nictitating membranes. In both cases, the visible third eyelid is temporary and should return to normal soon after the cat wakes up or fully recovers from sedation or anesthesia.

Haws syndrome

Haws syndrome describes the elevation of both third eyelids when there is no disorder of the eye or eye socket. Since the eye itself is healthy, cats with Haws syndrome do not have other eye-related symptoms. The cause of Haws syndrome in cats is unknown but is associated with stomach upset or gastrointestinal inflammatory disorders. Haws syndrome causes third eyelid protrusion in both eyes without signs of pain or other eye symptoms. GI symptoms, such as vomiting or diarrhea, may or may not be present. The prognosis for Haws syndrome is good, and the condition usually resolves by itself, though treatment for symptoms may still be needed. Repeated cases of Haws syndrome may indicate a chronic GI problem.

Eye infection or injury

Eye infections and injuries can cause a cat’s third eyelid to remain elevated. Most eye injuries and infections will have additional symptoms, such as reddened eyes, excessive squinting or blinking, or eye discharge. Occasionally, a minor eye infection or injury may have no other obvious symptoms outside of a raised third eyelid. A persistently elevated third eyelid may occur in association with:

• Corneal ulceration or scratches
• Conjunctivitis
• Eye irritants or foreign material in the eye

Conjunctivitis, or pink eye, is a common cause of an elevated third eyelid and is most frequently caused by viral respiratory infections.

Cherry eye

Cherry eye, or a prolapsed gland of the third eyelid, occurs when the tear gland that’s normally tucked down out of sight behind the third eyelid pops out of place. After it prolapses, the protruding gland is visible as a pink mass in the inside corner of the eye. The prolapsed gland pushes the eyeball back into its socket, causing the third eyelid to be abnormally exposed. Cherry eye is less common in cats than dogs and is not usually an emergency. However, prompt veterinary care is needed to prevent complications to the eye’s mucus membrane, such as dry eye or infection.

Horner’s syndrome

Horner’s syndrome is a collection of symptoms, including an elevated third eyelid, that points to a damaged or diseased sympathetic nervous system. Most cases of Horner’s syndrome affect only one side of the face, but it’s possible for the third eyelid in both eyes to be raised. Horner’s syndrome has other symptoms in addition to an elevated third eyelid, but they’re less obvious and may be overlooked. Symptoms of Horner’s syndrome include:

• Elevated third eyelid
• Constricted pupil
• Slight drooping of the upper eyelid
• Retraction of the eyeball into the head (enophthalmos)
• Increased pink color and warmth on the face

All of these symptoms affect the same eye and side of the face. Horner’s syndrome can be caused by a neck injury or other medical conditions that affect the nerves as they pass through the neck, but many cases are idiopathic with no known cause. The syndrome itself doesn’t usually need treatment, but its underlying cause might.

When a cat’s third eyelid is prominently visible, a vet usually does a complete physical, including a thorough eye examination. Diagnostic tests may be needed to rule out common health conditions and to find a definitive diagnosis. These tests may include:

• Fluorescein eye stain to check for ulcers and scratches
• Phenylephrine eye drops to test for Haws syndrome
• Special eye drops to stimulate different areas of the nervous system to identify the area of damage caused by Horner’s syndrome
• Bacterial or fungal culture
• Intraocular pressure test
• Blood tests
• Diagnostic imaging (x-rays, CT scan, MRI)

Treatment options vary depending on the underlying cause of the elevated third eyelid, but they may include:

• Eye medication with antibiotics, antifungals, or anti-inflammatories for injuries and infection
• Treatment of any stomach upset associated with Haws syndrome
• Addressing neurological disorders causing Horner’s syndrome
• Surgery for cherry eye

Not all causes of an elevated third eyelid require treatment. A temporary third eyelid protrusion when a cat is sleepy or recovering from anesthesia is normal. Haws or Horner’s syndrome may go away on their own without complications. A cherry eye may initially disappear then reappear, but surgery is eventually necessary to tack the gland back down in place.

It’s important to talk to a veterinarian any time you notice changes in your cat’s eyes, even if your cat seems fine otherwise. A persistently elevated third eyelid can indicate a cat is experiencing a health issue that requires medical attention for diagnosis and treatment. Online vets are an excellent tool to help with determining if your cat’s eyes appear normal. An online veterinary professional may also be able to identify other easily overlooked symptoms that point to an underlying health problem.

Is a raised third eyelid in cats an emergency?

A raised third eyelid with no other symptoms isn’t usually an emergency. However, prompt veterinary attention is warranted to diagnose the underlying cause of the elevated lid and to provide any necessary treatment. Prompt veterinary intervention helps prevent additional damage to the eye and treats underlying health issues that are causing the third eyelid to be elevated.

Why is my cat’s third eyelid showing, but they are acting normally?

A consistently raised third eyelid indicates either a problem with the eye itself or a systemic disease. Some of the health conditions that cause an elevated third eyelid don’t have other obvious symptoms. It’s normal for cats to have a temporarily raised third eyelid when they’re sleepy, right after they’ve woken up, and when they’re recovering from sedation or anesthesia. Most of the time when one or both of a cat’s third eyelids are especially visible, something is causing the cat’s eyeball to withdraw into the socket, such as pain or inflammation in the eye.

Is it normal for a cat’s third eyelid to show while sleeping?

It’s normal for a cat’s third eyelid to temporarily show when a cat is sleepy and right after they’ve woken up. If a cat’s eyelids are not fully closed while they’re in a deep slumber, the third eyelid may be visible. The third eyelid should not remain elevated after a cat is fully awake.

What is the normal appearance of a cat’s third eyelid?

A healthy third eyelid is a whitish-pink color and is only visible in the inner corner of a cat’s eye near the nose. The third eyelid briefly rises to protect the eye when the eyeball draws back into the socket in response to a potential injury, but it may remain persistently elevated in association with several different diseases.